(a) Technical Field
The present disclosure relates, in general, to a rotor for an interior permanent magnet (IPM) synchronous motor. In particular preferred embodiments, it relates to a rotor for an interior permanent magnet (IPM) synchronous motor for driving an air blower, in which the structure of the rotor is suitably modified to reduce magnetic flux leakage and, at the same time, maximize saliency ratio, thus improving the performance of the motor.
(b) Background Art
Rotors of electric motors are generally classified into surface-mounted permanent magnet (SPM) rotors and interior permanent magnet (IPM) rotors according to the position of permanent magnets.
Preferably, the SPM rotors are generally applied to most of high-speed motors (with a rotor shaft speed of more than 80 m/s) and, for example, as shown in FIG. 7, a retaining can 2 (or sleeve), which is a nonmagnetic material, is covered on the surface of permanent magnets 1 to prevent the permanent magnets from moving and ensure mechanical safety.
However, the high-speed motor in which the SPM rotor including the retaining can is applied causes an increase in the magnetic gap. Therefore, in order to satisfy the power required by the motor, the number of permanent magnets or coils used increases, or the size of the motor increases.
Accordingly, multi-layer IPM synchronous motors, in which permanent magnets are suitably inserted into the rotor in a multilayered manner, have been studied. However, such structures are rarely applied to the high-speed motors, and an important reason for this is that the space utilization for providing the IPM structure is reduced since the number of poles in the high-speed motors is limited to less than 4 poles. As a result, the magnetic flux leakage increases in a rotor core, and thus the efficiency of the motor decreases. Further, it is not easy to ensure sufficient mechanical strength against the stress exerted on the rotor core due to rotational force.
In certain examples where the multi-layer IPM rotor is applied to the high-speed motor, a space required to ensure mechanical safety, such as a rib, is increased, which reduces the space utilization and increases the magnetic flux leakage, thus making it suitably difficult to ensure the performance of the motor.
For example, as shown in FIG. 6, in a conventional 4-pole interior permanent magnet rotor, because the whole space of a flux barrier cannot be filled with a permanent magnet 1, there is a limitation in the space utilization. Moreover, in order to ensure mechanical safety during high-speed rotation, it is necessary to increase the distance between the respective flux barriers 1 and the distance between both ends of the flux barrier 3 and a rotor core 10, which corresponds to rib regions 4 and 5. Further, when the rib regions 4 and 5 are increased, the leakage of magnetic flux passing through the rib regions 4 and 5 increases, and thus it is difficult to ensure the performance of the motor.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.